The invention generally relates to a linear induction motor-operated downhole tool.
Valves typically are used in a well for such purposes as fluid flow control, formation isolation and safety functions. A common downhole valve is a hydraulically-operated valve, which is known for its reliable performance. However, hydraulically-operated valves have limitations.
For example, the use of a hydraulically-operated valve is depth-limited due to the high hydrostatic pressure acting against the valve at large depths, which may diminish the effective hydraulic pressure that is available to operate the valve. Furthermore, for deep applications, the viscous control fluid in a long hydraulic line may cause unacceptably long operating times for certain applications. In addition, a long hydraulic line and the associated connections provide little or no mechanism to determine, at the surface of the well, what is the true state of the valve. For example, if the valve is a safety valve, there may be no way to determine the on-off position of the valve, the pressure across the valve and the true operating pressure at the valve's operator at the installed depth.
Therefore, for some applications, an electrically-operated valve may be used in place of a hydraulically-operated valve. Conventional electrically-operated valves include solenoid-operated valves and complex motor-driven valves. Solenoids may be comparatively unreliable because they may require relatively high operating electrical currents and voltages to achieve the required levels of mechanical force and displacement. These factors exacerbate the problems with achieving reliable life of the valve, may stress electrical insulation and may require relatively complex controls and power sources to operate these devices.